Apparatus for use in aligning wheels

ABSTRACT

Toe measuring apparatus including a light projector unit and a photoelectric receiver suspended from a wheel clamp on each front wheel. Each projector projects a narrow vertical beam parallel to the wheel axis and onto the opposite receiver. Each receiver comprises a pair of photosensitive elements which are partially shaded and connected to provide a readout in accordance with the zone of impingement of the incident beam to indicate the toe angle of the opposite wheel.

United States Patent 11 1 Butler 1 1 APPARATUS FOR USE IN ALIGNINGWHEELS [75] Inventor: Louis L. Butler, Baton Rouge, La.

[73] Assignee: Bear Manufacturing Corp., Rock Island, 111.

[221 Filed: Nov. 19,1973

2| Appl. No.: 417,223

Related U.S. Application Data [63] Continuation of Ser. No. 234,814,March 15. 1972.

abandoned.

[52} U.S. Cl 356/155, 356/153, 356/152 [51] Int. Cl. G011) 11/00 {58]Field of Search 356/153, 152, 155, 156.

[56] References Cited UNITED STATES PATENTS 7/1968 MacMillan 356/155 X10/1970 Hopkins et a1 356/152 X IOL [4 1 Feb. 11,1975

3,603,688 9/1971 Smith-Vaniz 356/152 X 3,612,881 10/1971 King 356/172 X3.667.846 6/1972 Nater et a1 356/156 X OTHER PUBLICATIONS R. Barrett..1. of Physics E: Scientific Instruments, 1970, Vol. 3, pgs. 895-898.

Primary E.raminerRona1d L. Wibert Assistant Examiner-Paul K. Godwin [57]ABSTRACT Toe measuring apparatus including a light projector unit and aphotoelectric receiver suspended from a wheel clamp on each front wheel.Each projector projects a narrow vertical beam parallel to the wheelaxis and onto the opposite receiver. Each receiver comprises a pair ofphotosensitive elements which are partially shaded and connected toprovide a readout in accordance with the zone of impingement of theincident beam to indicate the toe angle of the opposite wheel.

20 Claims, 19 Drawing Figures PATENIEU 3.865.492

saw 2 or s PATENTED FEBI 1 1975 3. 865.492

SHEET u or 5 APPARATUS FOR USE IN ALIGNING WHEELS This is acontinuation, of application Serial No. 234,814 filed Mar. 15, 1972, nowabandoned.

This invention pertains to improvements in apparatus for use in aligningwheels on automotive vehicles, and particularly to apparatus utilized inmeasuring the toe angle.

Toe angle is a measure of the parallelism, or deviation from parallel,of opposed wheels, particularly steerable wheels, of a vehicle when in anominally straight-ahead position. This angle is an important factor intire wear as well as in the steering condition or steering stability ofthe vehicle.

Various arrangements have been proposed for use in measuring the toeangle of the wheels of automotive vehicles. Such devices have included,among others, mechanical linkage devices, optical telescope and targetarrangements, apparatus designed to measure the distances betweenreference points on the wheels, apparatus for measuring the angle ofdeviation between a reference device extending between the wheels and areference plane of the wheels, and arrangements for projecting lightbeams between apparatus attached to each of a pair of wheels. The lattertypes of devices have taken the form of projecting a scale image fromone device onto a screen of a device on the opposite wheel, with thescreen bearing a reference line. Other arrangements have been to providea scale on the screen and optically project a reference line from theopposite device onto the screen for comparison with the reference marks.

Prior devices of the various types referred to above exhibit variousproblems and shortcomings in use. Some of these devices inherently relyupon a readout by the operator at the measuring station, such as inreading a mechanical scale, or in reading a reference line against ascale on a screen in the optical projection type devices. Ambient lightalso can make it difficult to observe and accurately read theindications in projected image devices. Apparatus which requires theconnection of measuring devices or sensing devices between a pair ofwheels presents obvious disadvantages by way of requirements foroperator movement from station to station, avoiding interveningobstacles and the like. Also, various prior types of apparatus requiredprecompensation for other angles of the wheel system, such as the camberangle, before accurate measure ments can be made of the toe angle.

A primary requirement for apparatus for measuring the toe angle ofautomotive wheels is that of accuracy. Other important desirablecharacteristics include simplicity and convenience in applying theapparatus to successive vehicles and in obtaining the readings after theapparatus is applied, to avoid expenditure of excessive time by theoperator, and attendant costs. The apparatus should not requirerecalibration for each use and should minimize or avoid any requirementfor careful visual alignment by the operator in each successive use. andshould avoid the necessity of adjusting the device to accommodate eachparticular wheel position, e.g., camber angle, of each individualvehicle. The readout of the toe angle being measured should be presentedin a position where it can be observed conveniently by the operator, aswell as by the customer. Moreover, the readout should be easily readablewithout regard to ambient light levels.

it is an object of this invention to provide improved apparatus for usein the alignment of wheels of automotive vehicles and which overcomesproblems of the prior art and affords the desirable characteristics referred to above.

it is another object of this invention to provide wheel alignmentapparatus for accurately and reliably measuring the toe angle of wheelson automotive vehicles.

It is another object of this invention to provide improved apparatus ofthe type indicated wherein a predetermined desirable reference conditionbetween a pair of wheels can be established independently of thedistance between the two wheel units.

It is another object of this invention to provide im proved apparatus ofthe type indicated in which the readout of the sensing mechanism may bedisplayed for convenient observation by the operator and/or by thecustomer.

it is a further object of this invention to provide apparatus formeasuring toe angle which avoids requirements for compensatingadjustments due to other alignment characteristics of the wheels such ascamber.

It is another object of this invention to provide apparatus formeasuring toe angles and which is adjunctive to apparatus for measuringother alignment values, and particularly to provide an arrangementwhereby the toe measuring components may be brought into operationreadily and conveniently in conjunction with such other apparatus.

It is a further object ofthis invention to provide appa ratus of theindicated type which is integrated with a support assembly for thevehicles.

It is another object of this invention to provide im' proved apparatusmeeting the aforestated objects and which is of simple, rugged design,affords rapid toe measurements and is reliable and accurate inoperation.

In carrying out this invention in one illustrative form, toe anglemeasuring apparatus is provided comprising an optical projection systemwhich is suspended on a wheel of an automobile in a reference positionto project a narrow beam from a position adjacent the first wheel towarda target suspended on the opposite wheel, with the projection beingalong an axis parallel to the axis of rotation of the first wheel. Thetarget includes a pair of photosensitive elements connected to anindicator means, with the two photosensitive elements positioned anddesigned to provide outputs indicative of the position in which thelight beam impinges upon the receiver. In one advantageous embodiment,the light projection and photosensitive elements are supported in avehicle lift rack assembly in a manner to be freely movablelongitudinally of the rack, with detachable connector arms forconnecting each projector-receiver assembly to alignment apparatusattached to the wheel and positioning the projector-receiver assemblyparallel to the axis of rotation of the wheel,

For a more complete understanding of this invention reference should nowbe had to the embodiments illustrated in greater detail in the drawingsand described below by way of examples of the invention.

In the drawings, FIG. I is a schematic elevation view of the frontwheels of an automobile with apparatus employing teachings of thisinvention suspended from the wheels;

FIG. 2 is a schematic bottom view of the wheels of FIG. 1 showing oneprojector and one receiver of the measuring apparatus;

FIG. 3 is a side view of the assembly of FIG. I;

FIG. 4 is a schematic illustration of a photo-electrical system of themeasuring apparatus of FIG. 1;

FIG. 5 is an elevation view, partially in cross section, taken alongbroken line 55 of FIG. 6 and showing an other embodiment employingteachings of this invention;

FIG. 6 is a side view of the apparatus shown in FIG. 5;

FIG. 7 is a side view, taken generally along the line 77 of FIG. 5 andlooking in the direction of the arrows;

FIG. 8 is a bottom view of the sensing head subassembly, taken generallyalong the line 88 of FIG. 5 and looking in the direction of the arrows;

FIG. 9 is a partial sectional view taken along line 99 of FIG. 5 andlooking in the direction of the arrows;

FIG. 10 is a front view of the receiver subassembly of the apparatus inFIG. 5',

FIG. 11 is a sectional view taken along line llll of FIG. 10 and lookingin the direction of the arrows;

FIG. I2 is a view similar to FIG. 5 and illustrating another cmbodimentemploying teachings of this invention;

FIG. 13 is a partial side view, taken generally along line 13-13 of FIG.l2 and looking in the direction of the arrows;

FIG. 14 is a bottom view of the sensing head and mounting subassembly,taken generally along the line 14l4 of FIG. l2 and looking in thedirection of the arrows;

FIG. 15 is a partial side view, taken generally along line 15-15 of FIG.12 and looking in the direction of the arrows;

FIG. I6 is a schematic perspective view illustrating one manner ofstoring the connector subassembly of the apparatus of FIG. 12;

FIG. 17 is a schematic plan view of the light projectors and receiverunits in an aligned position; and

FIGS. 18 and 19 are views similar to FIG. 17 and illustrating themechanism in toe out and toe in positions, respectively.

In the drawings, 10 indicates a wheel of an automotive vehicle, with thesuffixes L and R applied wherever appropriate to designate a left frontwheel and a right front wheel, respectively.

In FIGS. I and 2, the apparatus shown mounted on each wheel comprises awheel clamp assembly I2, an adjustable checking head unit 14 pivotallyand rotatably mounted on the respective clamp assembly, and a toemeasuring unit 16 suspended on each of the heads 14. The illustratedwheel clamp assembly 12 is of the type having three mounting pins forclamping engagement with the outer bead of a wheel rim, to therebyprovide a fixed mounting reference with respect to the wheel assemblyand its axis of rotation. The wheel clamp assemblies may be of otherappropriate design for attaching a checking head 14 to a wheel asdescribed. The heads 14 also may be of any appropriate design,preferably including mechanism utilized in measuring other conditions ofwheel alignment, such as camber and caster angles. By way of furtherexample the components of each head 14 may comprise one or more gravitysensing electrolytic transducers as described in my copendingapplication entitled Apparatus For Determining Wheel Alignment." beingfiled herewith (Ser. No. 234,838, now abandoned, and parent applicationof Ser. No. 396,8l2, and/or one or more spirit level measuring devicesfor measuring such values.

The adjustable and pivotal mounting of each head unit 14 on therespective clamp assembly I2 also may be by any convenient construction.Referring for example to FIGS. 5 and I2, there is illustrated acompensator assembly 17 including a mounting block 18 affixed to thereference bar 120, with a compensator block 22 resiliently secured toblock 18 for rotation therewith as by spring mounting on threeequiangularly disposed studs 24. Thumb screws 26 adjust the longitudinalpositions of abuttment studs 27 for adjusting the angular position ofthe block 22 relative to block 18, and thus relative to the wheelassembly 10. Head 14 is rotatably supported on a bolt (not shown)extending from block 22 through a bearing assembly 28 and an appropriateopening in the adjacent wall of housing 29 of the unit I4. The opposedsurfaces of the block 22 and the housing 29 are firmly engaged againstopposite sides of the bearing 28. This fixes the axis of rotationalsupport of the head unit 14 relative to the wheel clamp 12, and thusrelative to the respective wheel assembly 10, subject only to suchselective angular adjustment as may be effected by adjusting the thumbscrews 26. Each assembly I2 is positioned with the compensator unitaligned with the spindle of the respective wheel 10, whereby the axis ofrotation of the unit 14 on the assembly I2 is essentially aligned withthe axis of rotation of the wheel.

Referring now to FIGS. I and 4, each unit I6 includes a light projectorassembly 30 and a receiver 32. Each assembly 30 includes a clear glasslight bulb 34 having a filament 36 in the form of a vertical helix ofsubstantial length and relatively small diameter. A pair of shields 38are positioned in front of the bulb 34, and spaced to provide a narrowprojection slot 40. A double convex lens 42 is positioned between thebulb 34 and the shields 38 in alignment with the slot 40, to focus theimage of the filament 36 as a narrow light beam onto the receiver 32, asindicated by the rectangle 44. Receiver 32 includes two photosensitiveele ments 46 and 48, such as selenium photovoltaic plates. These platesare of the type to provide an electrical output signal directly relatedto the quantity of light energy impinging upon the respective plate. Amasking plate 49 overlies the two plates 46 and 48, and has openings 49aand 49b of triangular configuration, with the points of the trianglesspaced apart approximately the width of the projected light image 44.

The two plates 46 and 48 are connected to appropriate sensing andindicator means, such as a midpoint meter 50, in opposing relation toone another to deflect the meter indicator 5] in one direction from itsmidpoint upon photoactuation of one of the elements 46 and 48, and todeflect the indicator in an opposite direction upon photoactuation ofthe other element. With the narrow light beam centered between the V-shaped openings as illustrated, or overlapping the two openings in equalamounts. the meter indicator will re main at its midpoint or zero"position. If the light source 30 is pivoted to move the projected imageto the right or left, a greater potential will be provided by the plateelement 46 or 48 onto which the light moves, thereby providing acorresponding indication on the meter 50.

It will be observed that the light image on the receiver 32 is of awidth substantially less than the horizontal width of the exposedportion of each photosensitive element 46 and 48. Also, the light energyper unit area is essentially uniform throughout the area of theprojected image. However, the vertical dimension of the area of anelement 46 or 48 upon which the light beam impinges through therespective opening 490 or 49b will increase as the beam moves from thecenter of the receiver toward either outer edge, in accordance with theconfiguration of the openings. With triangular exposed areas asillustrated, this variation of area is in linear relation to thedistance of the image from the center position. Thus, as the angularposition of the light source 30 is changed, causing the image 44 to moveto the right or left on the target 32, the output from thephotosensitive elements will vary in accordance with the displacement ofthe beam image from the center position. Accordingly, a direct readoutmay be obtained on meter 50 of the change in angular position of theaxis of the projector unit 30.

Referring again to FIGS. 1 and 2, each compensator 17 is adjusted as thewheel is rotated, to obtain a steady reading on a level sensing devicein the unit 14. This compensates for run out" or variations in thewheel, in a known manner, so that the mounting axis or axis of rotationof the unit l4 on the wheel clamp 12 is parallel to the axis of rotationof the respective wheel. The wheel is then positioned with the referencebar 120 vertical, and with the weight of the vehicle on the wheel. Thisinsures that the axis of rotational support of the unit 14 on theassembly 12 is in a vertical plane through the axis of rotation of thewheel. Each head 16 is suspended as a pendulum on the respective unit 14by a mounting arm 54. The arm 54 maintains the unit 16 in a positionsuch that the axis of projection of each light source is parallel to theaxis of rotation of the respective head 14 on the wheel clamp 12 andthus parallel to the axis of rotation of the respective wheel. Moreoverdue to the pendulum suspension, each unit 16 will inherently assume aposition directly beneath the respective unit l4. Thus the axis ofprojection of the unit 16 also will be in vertical alignment with theaxis of rotation of the wheel.

The axes of rotation of the front wheels of an automobile areessentially colinear at zero toe angle, i.e., each wheel in straightahead position (except for exceptional instances, such as a bent frameresulting from an accident). Accordingly, the two noted vertical planesof the wheel axes and the respective projectors 30 will be coincident,with each light beam being centered on the receiver 32 of the oppositeunit 16 at zero toe angle, as illustrated schematically in FIG. 17. If awheel is in a toe out condition, the beam from the light source 30attached to that wheel will strike the opposite receiver 32 at a pointon a plate 48 displaced from the center area in proportion to the angleof toe out and the distance between the light source and the receiver.For instance, FIG. 18 illustrates schematically the position of the twounits where both wheels are in a toe out position (the front of thevehicle is towards the top of the drawing). Similarly, at toe in angles,each light beam will impinge upon the other photocell 46 of the receiverat a point displaced from the center point in proportion to the angle oftoe in and the distance between the light source and the receiver asseen in FIG. 19.

It will be appreciated that the readout circuitry and meter may have avariable calibration element for adjustment in accordance with the wheelspacing of the vehicle. Alternatively, the circuitry can be calibratedto a standard wheel width, with interpolation, as by appropriate tablesor calculation, when testing an automobile of a different wheel spacing.

Thus, with the described units 16 mounted as described, the toe anglesof the wheels may be read directly from meters 50, and be accuratelyadjusted with respect to those meters. Moreover, the meters may beplaced in any suitable and convenient locations.

One advantage of the illustrated apparatus is that the center referenceor zero position illustrated in FIG. 17 is independent of the spacingbetween the light sources 30 and targets 32, and thus independent of thewheel spacing. Accordingly, the toe angle ofa vehicle may be calibratedto a desired value without regard to the wheel spacing by firstpresetting each of the units 16 at the desired toe angle to the axis ofrotation of the respective wheel, and then adjusting the wheels untilthe toe measuring mechanism is aligned as in FIG. 17. At that point thewheels will be at the predetermined desired toe angle. Specific examplesof apparatus for effecting such a predetermined setting will bediscussed below with respect to the embodiments of FIGS. 5 and 12.

By mounting the units l6 to extend toward the planes of or beneath thewheels, the receivers 32 are near the steering axis of each wheel.Accordingly, the displacement of the receiver from the desired referencepositions at various toe angle settings is minimized. Moreover, thesmall angles involved and the magnification factor of projection acrossthe width of the automobile also reduce the significance of any suchdisplacement of the receivers.

FIGS. 5-11 illustrate a preferred embodiment of the inventionincorporated in a lift rack assembly such as is often utilized at wheelalignment stations. Only one trackway 60 and associated toe anglemeasuring mechanism is illustrated in these drawings, it being understood that a corresponding track and corresponding toe measuringmechanism also are provided at the opposite side of the vehicle, withthe two angle measuring mechanisms cooperating as described above withrespect to the embodiment of H08. 14.

The illustrated rack 60 is basically channel-shaped, including thevehicle supporting web 62 and a pair of downwardly extending outerflanges 64 and 66, each provided with a return bent flange section 68,at its lower edge. A J-shaped reinforcing flange 72 extends along theinner flange 64. A support bracket 74 extends downward from the midareaof the web 62. Referring also to FIG. 6, during checking and adjustmentof the alignment of the front wheels, those wheels preferably arepositioned on turning radius plates 76 which are ro tatably journaled bybearings 78 atop support plates 80 mounted on bearing rollers 82 forrelatively free movement transverse to the trackways 60. A locking pin84 is provided for locking the plates 76 and 80 in a predeterminedposition on the rack 60 as desired. The relative movement permitted bythe plates 76 and 80 as sures easy movement of the wheels during thealignment procedures to avoid erroneous readings as might otherwise beintroduced because of forces generated by the frictional engagement ofthe lower surfaces of the tires with fixed support surfaces.

In this embodiment, a light bulb 34 and a combination lens-photocellunit 86 are supported within the cavity defined by the trackway 60. Asseen in FIG. 5, the light bulb 34 is mounted on a bracket 88 which isattached to the unit 86. A shaft 90 extends from the opposite side ofthe unit 86 through a roller 92 which has rolling engagement with thedistal edge of flange 68 for supporting the outer end of the assembly. Asquare tubular support member 94 is attached to bracket 88 and extendsthrough an elongated slot 96 in support bracket 74 and an aligned slot98 in the flange 66. A similar slot 100 is provided through the flange64 and the flange 72 in axial alignment with the light source. Each ofthe described slots is elongated horizontally, as illustrated by slots98 and 100 in FIGS. 6 and 7 to permit lateral movement of the assemblyas described below.

Referring to FIGS. and 11, the unit 86 includes a mounting block 104having shallow recesses 106 for receiving the sensitive plates 46 and48. The plates are positioned to leave a narrow aperture 108therebetween. The lens 42 is mounted directly behind this aperture.Thus, the aperture 108 serves both as the aperture for shaping the lightbeam directed at the similar receiver unit 86 mounted at the oppositewheel station and as the center or zero target area for the light beamprojected from that opposite unit. A cover plate or plates 110 aresecured to the front surface of the block 104, as by screws 112, toclamp the plates 46 and 48 in position. As shown in FIG. 10 these platesdefine opposed V-shaped openings 114 and 116 in alignment with oneanother and each having its apex at the edge of the lens aperture 108.

Referring to FIGS. 5, 8 and 9, a short hollow tubular member 118 isattached to the underside of the checking head I4, along the center lineof the unit 14 and essentially parallel to the axis of rotationalsupport of this unit on the compensator 17. The member 118 is mounted ina manner to permit setting of a predetermined toe angle value, asreferred to above. To this end, a shouldered stud I extends through anappropriate opening in one end of the bar 118, and is threaded into theunderside of the housing 29 of unit 14 to pivotally mount the inner endof the bar. The outer end of bar 118 is received in a U-shaped support122 which is secured to the housing 29, as by screws 124. A pair ofthumb screws 126 and 128 extend through the vertical legs 129a and I29bof the support 122 and abut the opposite sides of the bar 118 forselective angular adjustment of the bar relative to the unit 14.Referring particularly to FIG. 8, a further adjustment screw 130 isprovided on the side of the bar 118 which would correspond to a toe outsetting, and is preadjusted and locked at a zero toe angle position by alocking screw I32. The screw 130 is included as a safety measure againstinadvertently setting the bar 118 for a toe out angle when arranging theillustrated apparatus for a predetermined toe setting as describedabove.

An articulated connector linkage 134 connects the checking unit 14 andthe toe angle sensing unit. The linkage 134 comprises a square bar 136for mating telescopic engagement in member 118, another square bar 138for similar telescopic mating engagement in the member 94, and a pair ofrigid interconnecting links 140 and 142. The bars I36 and 138 and links140 and 142 are joined by connectors 144, each designed to permitfolding angular adjustment of the connected el- 5 ements in onepredetermined plane, without permitting relative movement transverse tothat plane. By way of example, each connector 144 includes a largeplatelike.,element 146 rigidly joined to one link at the respectivejoint, an opposing plate-like element 148 rigidly joined to the otherlink connected to the same joint, a large brass bearing washer 150between the opposing surfaces of these plate-like elements, and a pivotbolt 152 which maintains this subassembly in snug faceto-face abuttingrelationship. Such a subassembly permits the aforementioned angularadjustment about the axis of bolt 152, without permitting relativemovement transverse to the plane of the washer I50. The matingengagements of the square bars 136 and 138 in the components 94 and 118insure the maintenance of the indicated coplanar arrangement between thelinkage 134 and the connected components. Thus, with the linkage 134connected between the members 94 and 118, the toe sensing unit 34, 86 isconnected to the sensing head 14 in a manner to maintain the projectionaxis of the unit 34, 86 in a plane parallel to the refer ence pivot axisof the head 14.

The toe sensing unit 34, 86 is freely movable longitudinally of the rackalong slots 96 and 98 and over the surface of flange 68. Thus, the unit34, 86 is freely movable to preserve the pendulum action of the sensinghead 14 to remain in the vertical plane through the sensing head axis.The noted vertical alignment is further enhanced in that the slot 98 isof a vertical depth only sufficient to permit free lateral slidingmovement of the bar 94, and precludes rotational movement of that bar inthe slot. Vertical positioning of the entire unit also can be checked byan appropriate level sensing device in the head 14, if desired.

In operation, a pair of toe measuring units as illustrated in FIGS. 5-11function in the same manner described above with respect to theembodiment of FIGS. l-4. In addition, it will be appreciated that thisunit is permanently housed in the lift rack 60. This rack may be on ahoist mechanism, or may be a permanent floor fixture on which thevehicle is positioned for checking its alignment. Moreover, the simpletelescopic mating engagement of the bars 136 and 138 with the elements118 and 94 permit quick and simple disconnection and reconnection of thetoe measuring unit 34, 86 to the checking head 14. Thus, the head 14 maybe utilized for measuring camber, caster or other angles in a normalmanner during part of the alignment procedure, with the toe sensing unit34, 86 being quickly connected for checking the toe angle.

Thumb screws 126 and 128 may be calibrated for setting preselected toeangles, if desired.

The vertical height of the light beam projected from a source 30 to areceiver 32 or 86 may be of a vertical dimension significantly greaterthan the vertical height of the photosensitive units 46 and 48, such asto avoid any necessity for careful alignment of the units vertically.This light beam may be concentrated for increasing the sensitivity andoutput of the photosensitive units by positioning an elongated lens ormagnifying strip 154 over the slot 100 as shown in FIG. 5 and by dashedlines in FIG. 7. Such a device will concentrate a greater amount of thelight energy on the photosensitive plates without changing the width ofthe light beam and thus without adversely affecting the accuracy.

The embodiment illustrated in FIGS. 12-15 includes superposed lightsource and target components similar to those disclosed in FIGS. 1-3, ina trackway assembly similar to the embodiment of FIGS. -11. Again, asingle unit is shown on one wheel, it being understood that acorresponding unit is provided at the opposite wheel.

in FIG. 12, the rack 160 includes downwardly extending flanges 162 and164 provided with elongated slots 166 and 168 for receiving rollers 170and 172 of the support bar 174. The light source subassembly 30 andreceiver unit 32 are mounted in a single housing 176 pivotally suspendedfrom the bar 174 as illustrated. Elongated slots 178 and 180 areprovided in the flange 164 for projection and reception passage of thelight beam of the respective units 30. The various slots 166, 168, 178and 180 are of sufficient length to permit the requisite adjustment ofthe supports and of the light source and receiver longitudinally of therack in accordance with the toe angle of the wheel unit 10.

Referring to FIGS. 12 and 14, the connecting and adjusting arrangementon the base of the checking unit 14 in this embodiment comprises a bar182 provided with a circular recess for pivotal engagement on a stud 184projecting downward from the underside of the housing 29 of unit 14. Ata spaced position, near its forward end, bar 182 is provided with a slot186 for lateral sliding engagement with a second stud 188 projectingdownward from the support housing 29. A thumb screw 192 extends throughthe bar 182 and is threaded into the underside of the housing 29 forsupporting the bar 182 on the housing. Lateral angular positioning ofthe bar 186 for setting preselected toe angles is provided by a pair ofthumb screws 194 and 196 which are threaded laterally through the bar182 and abut the fixed stud 188. it will be appreciated that appropriateadjustment of these screws will adjust the angular position of bar 182about the pivot point of stud 184, and lock the bar in any preselectedposition. within the ambit permitted by the length of slot 186.

A pointer 198 may be provided on the outer end of the bar 182 forcorrelation with indicia 200on the outer end of the support housing as areference for presetting the bar 182 for predetermined toe angles.

An articulated linkage 202 joins the inner end of bar 182 with the outerend of rod 174. The linkage 202 is designed to permit foldingarticulation in a predetermined plane, without permitting relativerotation between the components transverse to that plane, in the samemanner referred to above in discussing linkage 134. The toe measuringcomponents are readily disconnected from the head 14 by simplyunscrewing thumb screw 192, and removing the bar l82,from housing 29.The linkage components may be stored conveniently by securing them inclips along the side of the rack as illustrated schematically in FIG.[6. Concomitantly, these units may be reconnected by the simpleexpedient of repositioning the bar 182 on the studs 184 and 186, andsecuring the thumb screw 192, for subsequent measurements.

In the embodiments of FIGS. 5-16 the two light projector units andreceiver units are at predetermined spacings regardless of variations inthe wheel spacings of the vehicles being tested. The articulatedconnecting linkages 134 and 202 provide the desired connections andalignment with the respective wheels regardless of the positions of thewheels across the width of the rack supports. Also, the projector andreceiver components are disposed beneath the wheels and in or very closeto the steering axes. These factors facilitate accurate calibration ofthe units and accuracy of the measurements.

In each embodiment, flexibility is provided for utilizing the wheelclamp and checking head 14 in measuring other alignment values, withconvenient connection of the illustrated apparatus for the toe anglemeasurements.

Various types of photosensitive devices may be utilized as units 46 and48, such as photoconductive or photovoltaic units. Moreover, the meter50 may be a milliammeter or galvanometer type device, or otherappropriate indicator, in accordance with the type of photosensitiveunits and the circuitry utilized to sense the response of those units.However, shaded photovoltaic plates connected directly to a meter 50provide a very simple design and is preferred. In one specificillustrative embodiment of the receiver unit, a pair of rectangularselenium photovoltaic plates were utilized successi'ully with a 12 volt,20 watt BA l2l5 clear glass light bulb. The photovoltaic plates weremodel S LB units obtained from Vactec Inc. of Maryland Heights,Missouri, each plate being about l-ll/l6 inches long and seven-eighthsinch wide (vertical dimension as installed). The receiver unit was about45 inches from the light source unit 30. A centerpoint mil liammeter ofa scale 250-0-250 milliamps was utilized, and an output of nearly 250milliamps was indicated without the intensifier unit 154. By applying abar 154 as a light collector a much greater output reading wasavailable.

It will be appreciated that various types of light sources andcompatible photoresponsive receiver units may be utilized for theprojector and receiver devices in the aforedescribed apparatus. By wayof a further specific example, for enhanced accuracy, each lightprojector may be of the laser type to project a laser beam to anappropriate receiver on the opposite sensing unit.

It will be apparent to those skilled in the art that other modificationsand embodiments of the specific apparatus disclosed herein may be madewithout departing from the spirit and scope of this invention.Particular construction and fabrication details of several embodimentsare disclosed only by way of example, and the various components may befabricated and assembled in other configurations.

It will be seen that improvements have been provided which meet theaforestated objects.

While particular embodiments of this invention are shown and describedherein, it will be understood, of course, that the invention is notlimited thereto, since many other modifications may be made by thoseskilled in the art, particularly in light of the teachings herein. It iscontemplated, theretore, by the appended claims to cover any suchmodifications as fall within the true spirit and scope of thisinvention.

What is claimed is:

1. Apparatus for use in aligning vehicle wheels comprising means forprojecting a directional beam of light, means for attaching saidprojecting means to a first wheel for projecting said directional beamwith the longitudinal axis of said beam in predetermined angularrelationship to a line generally parallel to the axis of rotation ofsaid first wheel, said line lying in a generally vertical plane throughthe axis of rotation of said first wheel, and photosensitive meanspositioned to intercept said beam when such axis of rotation is within arange predetermined positions, and means responsive to saidphotosensitive means for indicating the position of said axis ofrotation relative to a predetermined reference position.

2. Apparatus as in claim 1 wherein said projecting means is positionedfor projecting said beam parallel to the axis of rotation of said wheel.

3. Apparatus as in claim 1 wherein said attaching means includes meansfor engaging such a wheel, a support rotatably journalled on saidengaging means and adjustable to have its axis of rotation parallel tothe axis of rotation of the engaged wheel, said projecting means andsaid photosensitive means being suspended from said support.

4. Apparatus as in claim 3 wherein said projecting means and saidphotosensitive means extend toward the plane of such wheel from thesuspension support.

5. Apparatus as in claim I wherein said attaching means includes meansfor engaging such a wheel, a support rotatably suspended on saidengaging means, means for adjusting said support to position its axis ofrotational suspension parallel to the axis of rotation of the engagedwheel, said projecting means and said photosensitive means beingpositioned beneath the posi' tion of such an engaged wheel, and meansconnecting said support to said projecting means and photosensitivemeans for positioning said projecting means and said photosensitivemeans along an axis parallel to said axis of rotational suspension.

6. Apparatus as in claim 5 including a wheel support, said projectingmeans and said photosensitive means being disposed in said wheelsupport.

7. Apparatus as in claim 1 wherein said photosensitive means provides aresponse signal which varies in accordance with the zone thereof onwhich said beam of light impinges.

8. Apparatus as in claim 1 wherein said photosensitive means comprisesone photosensitive unit positioned to intercept said beam of light whensaid beam is on one side of a predetermined reference position, andanother photosensitive unit positioned to intercept said beam of lightwhen said beam is on the opposite side of such reference position.

9. Apparatus as in claim 8 wherein each of said photosensitive units isprovided with an exposed area which varies in height with the distancefrom such reference position.

l0. Apparatus as in claim 9 wherein each of said units is aphotoresponsive plate, and a shield over said plate provided with a pairof spaced triangular openings.

ll. Apparatus as in claim 10 wherein each of said units is aphotovoltaic plate.

I2. Apparatus as in claim I wherein said projecting means is adapted toproject a beam of limited horizontal width, said photosensitive meansaffording an exposed photosensitive area of greater horizontal widththan the width of said beam, and said exposed area varying in verticalheight across its width.

13. Apparatus for use in measuring the toe of vehicle wheels comprisingfirst and second sensing units, each of said units including means forprojecting a directional light beam, means for supporting said units onopposed wheels of a vehicle with said projecting means of each unitprojecting its directional beam toward the other of said units inpredetermined angular relationship to a line generally parallel to theaxis of rotation of said first wheel, said line lying in a generallyvertical plane through the axis of rotation of the wheel on which therespective projecting unit is supported, and each of said sensing unitsincluding photosensitive means responsive in accordance with theposition in which said beam projected by the other said sensing unitimpinges thereon for indicating the position of said axis of rotationrelative to a predetermined reference position.

14. Apparatus as in claim 13 wherein said supporting means for each ofsaid units includes means for engaging such a wheel, a support rotatablyjournalled on said engaging means and adjustable to have its axis ofrotation parallel to the axis of rotation of the engaged wheel, and saidprojecting means and said photosensitive means of each of said unitsbeing suspended from the respective support.

15. Apparatus as in claim 13 wherein said supporting means for each ofsaid units includes means for engaging such a wheel, a support rotatablysuspended on said engaging means, means for adjusting said support toposition its axis of rotational suspension parallel to the axis ofrotation of the engaged wheel, said projecting means and saidphotosensitive means of the respective units being positioned beneaththe position of such an engaged wheel, and means connecting said supportto said projecting means and photosensitive means for positioning saidprojecting means and said photosensitive means along an axis parallel tosaid axis of rotational suspension.

16. Apparatus as in claim 13 wherein said photosensitive means of eachof said units provides a response signal in accordance with the zonethereof on which said beam of light projected by the other of said unitsimpinges.

17. Apparatus as in claim 13 wherein said projecting means of each ofsaid units is adapted to project a light beam of limited horizontalwidth and of a vertical height greater than the height of saidphotosensitive means of the other of said units, and each of saidphotosensitive means affording an exposed photosensitive area of greaterhorizontal width than the width of said beam projected by the other ofsaid units. said exposed area varying in vertical height across itswidth.

18. Apparatus for use in aligning wheels of automotive vehiclescomprising a support rack for supporting each front wheel of such avehicle, first and second sensing units mounted in said rack with one ofsaid units beneath the position assumed by each front wheel on saidsupport rack, each of said sensing means including means for projectinga directional beam of light and photosensitive means responsive to sucha beam received from the other of said units, means for positioning eachof said sensing units with the axis of projection of such directionalbeam therefrom at a predetermined angle to a line generally parallel tothe axis of rotation of said first wheel, said line lying in a generallyvertical plane through the axis of rotation of the respective adjacentwheel and for positioning said photosensitive means of said unit tointercept said beam from the other of said sensing units, and meansresponsive to each of said photosensitive means for indicating theposition of the received beam relative to a predetermined referenceposition.

a support rotatably suspended on said clamp assembly and adjustable tohave its axis of rotation parallel to the axis of rotation of suchwheel, and an articulated linkage connected to said supports and to therespective sensing unit, said linkage permitting free adjustmentmovement of said support about its axis of rotation and maintaining therespective sensing unit parallel to said axis during such movement.

1. Apparatus for use in aligning vehicle wheels comprising means forprojecting a directional beam of light, means for attaching saidprojecting means to a first wheel for projecting said directional beamwith the longitudinal axis of said beam in predetermined angularrelationship to a line generally parallel to the axis of rotation ofsaid first wheel, said line lying in a generally vertical plane throughthe axis of rotation of said first wheel, and photosensitive meanspositioned to intercept said beam when such axis of rotation is within arange predetermined positions, and means responsive to saidphotosensitive means for indicating the position of said axis ofrotation relative to a predetermined reference position.
 2. ApparatuS asin claim 1 wherein said projecting means is positioned for projectingsaid beam parallel to the axis of rotation of said wheel.
 3. Apparatusas in claim 1 wherein said attaching means includes means for engagingsuch a wheel, a support rotatably journalled on said engaging means andadjustable to have its axis of rotation parallel to the axis of rotationof the engaged wheel, said projecting means and said photosensitivemeans being suspended from said support.
 4. Apparatus as in claim 3wherein said projecting means and said photosensitive means extendtoward the plane of such wheel from the suspension support.
 5. Apparatusas in claim 1 wherein said attaching means includes means for engagingsuch a wheel, a support rotatably suspended on said engaging means,means for adjusting said support to position its axis of rotationalsuspension parallel to the axis of rotation of the engaged wheel, saidprojecting means and said photosensitive means being positioned beneaththe position of such an engaged wheel, and means connecting said supportto said projecting means and photosensitive means for positioning saidprojecting means and said photosensitive means along an axis parallel tosaid axis of rotational suspension.
 6. Apparatus as in claim 5 includinga wheel support, said projecting means and said photosensitive meansbeing disposed in said wheel support.
 7. Apparatus as in claim 1 whereinsaid photosensitive means provides a response signal which varies inaccordance with the zone thereof on which said beam of light impinges.8. Apparatus as in claim 1 wherein said photosensitive means comprisesone photosensitive unit positioned to intercept said beam of light whensaid beam is on one side of a predetermined reference position, andanother photosensitive unit positioned to intercept said beam of lightwhen said beam is on the opposite side of such reference position. 9.Apparatus as in claim 8 wherein each of said photosensitive units isprovided with an exposed area which varies in height with the distancefrom such reference position.
 10. Apparatus as in claim 9 wherein eachof said units is a photoresponsive plate, and a shield over said plateprovided with a pair of spaced triangular openings.
 11. Apparatus as inclaim 10 wherein each of said units is a photovoltaic plate. 12.Apparatus as in claim 1 wherein said projecting means is adapted toproject a beam of limited horizontal width, said photosensitive meansaffording an exposed photosensitive area of greater horizontal widththan the width of said beam, and said exposed area varying in verticalheight across its width.
 13. Apparatus for use in measuring the toe ofvehicle wheels comprising first and second sensing units, each of saidunits including means for projecting a directional light beam, means forsupporting said units on opposed wheels of a vehicle with saidprojecting means of each unit projecting its directional beam toward theother of said units in predetermined angular relationship to a linegenerally parallel to the axis of rotation of said first wheel, saidline lying in a generally vertical plane through the axis of rotation ofthe wheel on which the respective projecting unit is supported, and eachof said sensing units including photosensitive means responsive inaccordance with the position in which said beam projected by the othersaid sensing unit impinges thereon for indicating the position of saidaxis of rotation relative to a predetermined reference position. 14.Apparatus as in claim 13 wherein said supporting means for each of saidunits includes means for engaging such a wheel, a support rotatablyjournalled on said engaging means and adjustable to have its axis ofrotation parallel to the axis of rotation of the engaged wheel, and saidprojecting means and said photosensitive means of each of said unitsbeing suspended from the respective support.
 15. Apparatus as in claim13 wherein said supporting means for each of said units includes meAnsfor engaging such a wheel, a support rotatably suspended on saidengaging means, means for adjusting said support to position its axis ofrotational suspension parallel to the axis of rotation of the engagedwheel, said projecting means and said photosensitive means of therespective units being positioned beneath the position of such anengaged wheel, and means connecting said support to said projectingmeans and photosensitive means for positioning said projecting means andsaid photosensitive means along an axis parallel to said axis ofrotational suspension.
 16. Apparatus as in claim 13 wherein saidphotosensitive means of each of said units provides a response signal inaccordance with the zone thereof on which said beam of light projectedby the other of said units impinges.
 17. Apparatus as in claim 13wherein said projecting means of each of said units is adapted toproject a light beam of limited horizontal width and of a verticalheight greater than the height of said photosensitive means of the otherof said units, and each of said photosensitive means affording anexposed photosensitive area of greater horizontal width than the widthof said beam projected by the other of said units, said exposed areavarying in vertical height across its width.
 18. Apparatus for use inaligning wheels of automotive vehicles comprising a support rack forsupporting each front wheel of such a vehicle, first and second sensingunits mounted in said rack with one of said units beneath the positionassumed by each front wheel on said support rack, each of said sensingmeans including means for projecting a directional beam of light andphotosensitive means responsive to such a beam received from the otherof said units, means for positioning each of said sensing units with theaxis of projection of such directional beam therefrom at a predeterminedangle to a line generally parallel to the axis of rotation of said firstwheel, said line lying in a generally vertical plane through the axis ofrotation of the respective adjacent wheel and for positioning saidphotosensitive means of said unit to intercept said beam from the otherof said sensing units, and means responsive to each of saidphotosensitive means for indicating the position of the received beamrelative to a predetermined reference position.
 19. Apparatus as inclaim 18 wherein each of said sensing units is supported in said rackfor horizontal adjusting movement, said positioning means including anarticulated linkage for connecting each of said sensing units to anattachment assembly mounted on the respective superposed wheel. 20.Apparatus as in claim 18 wherein said means for positioning each of saidsensing units includes a wheel clamp assembly attached to the respectivefront wheel, a support rotatably suspended on said clamp assembly andadjustable to have its axis of rotation parallel to the axis of rotationof such wheel, and an articulated linkage connected to said supports andto the respective sensing unit, said linkage permitting free adjustmentmovement of said support about its axis of rotation and maintaining therespective sensing unit parallel to said axis during such movement.